Resolution Changes On Reboot!!!

hey guys,
I recently changed my HTPC motherboard to the Asus M3N78-VM which works great. However everytime I restart the HTPC the refresh rate changes from 50Hz to 60Hz which is no good as I only watch 50Hz content so I get alot of judder. This is under vista with the 190 drivers (not sure the exact revision but it is 190.xx). In the nvidia control panel the native resolution which is what I want (1080p @ 50Hz) however the recommended resolution is what it reverts to on restart (1080p @ 60Hz). Does anyone know how to force the resolution to the native because otherwise I have to plug in a mouse everytime I turn the htpc to change the res back. Its been driving me nuts so hopefully someone has an idea of how to fix it. Btw its connected via hdmi so pulling out certain pins from a dvi cable is no good.
Cheers.